#region .NET Disclaimer/Info

//===============================================================================
//
// gOODiDEA, uland.com
//===============================================================================
//
// $Header :		$  
// $Author :		$
// $Date   :		$
// $Revision:		$
// $History:		$  
//  
//===============================================================================

#endregion

#region Java

/**
 * Class GifDecoder - Decodes a GIF file into one or more frames.
 * <br><pre>
 * Example:
 *    GifDecoder d = new GifDecoder();
 *    d.read("sample.gif");
 *    int n = d.getFrameCount();
 *    for (int i = 0; i < n; i++) {
 *       BufferedImage frame = d.getFrame(i);  // frame i
 *       int t = d.getDelay(i);  // display duration of frame in milliseconds
 *       // do something with frame
 *    }
 * </pre>
 * No copyright asserted on the source code of this class.  May be used for
 * any purpose, however, refer to the Unisys LZW patent for any additional
 * restrictions.  Please forward any corrections to kweiner@fmsware.com.
 *
 * @author Kevin Weiner, FM Software; LZW decoder adapted from John Cristy's ImageMagick.
 * @version 1.03 November 2003
 *
 */

#endregion

using System;
using System.Collections;
using System.Drawing;
using System.IO;

namespace CloudShot.Utils.Encoding
{
  public class GifDecoder
  {
    /**
		 * File read status: No errors.
		 */
    public static readonly int STATUS_OK = 0;

    /**
		 * File read status: Error decoding file (may be partially decoded)
		 */
    public static readonly int STATUS_FORMAT_ERROR = 1;

    /**
		 * File read status: Unable to open source.
		 */
    public static readonly int STATUS_OPEN_ERROR = 2;
    protected static readonly int MaxStackSize = 4096;

    protected Stream inStream;
    protected int status;

    protected int width; // full image width
    protected int height; // full image height
    protected bool gctFlag; // global color table used
    protected int gctSize; // size of global color table
    protected int loopCount = 1; // iterations; 0 = repeat forever

    protected int[] gct; // global color table
    protected int[] lct; // local color table
    protected int[] act; // active color table

    protected int bgIndex; // background color index
    protected int bgColor; // background color
    protected int lastBgColor; // previous bg color
    protected int pixelAspect; // pixel aspect ratio

    protected bool lctFlag; // local color table flag
    protected bool interlace; // interlace flag
    protected int lctSize; // local color table size

    protected int ix, iy, iw, ih; // current image rectangle
    protected Rectangle lastRect; // last image rect
    protected Image image; // current frame
    protected Bitmap bitmap;
    protected Image lastImage; // previous frame

    protected byte[] block = new byte[256]; // current data block
    protected int blockSize = 0; // block size

    // last graphic control extension info
    protected int dispose = 0;
    // 0=no action; 1=leave in place; 2=restore to bg; 3=restore to prev
    protected int lastDispose = 0;
    protected bool transparency = false; // use transparent color
    protected int delay = 0; // delay in milliseconds
    protected int transIndex; // transparent color index

    // max decoder pixel stack size

    // LZW decoder working arrays
    protected short[] prefix;
    protected byte[] suffix;
    protected byte[] pixelStack;
    protected byte[] pixels;

    protected ArrayList frames; // frames read from current file
    protected int frameCount;

    /**
		 * Gets display duration for specified frame.
		 *
		 * @param n int index of frame
		 * @return delay in milliseconds
		 */

    public int GetDelay(int n)
    {
      //
      delay = -1;
      if ((n >= 0) && (n < frameCount))
      {
        delay = ((GifFrame)frames[n]).delay;
      }
      return delay;
    }

    /**
		 * Gets the number of frames read from file.
		 * @return frame count
		 */

    public int GetFrameCount()
    {
      return frameCount;
    }

    /**
		 * Gets the first (or only) image read.
		 *
		 * @return BufferedImage containing first frame, or null if none.
		 */

    public Image GetImage()
    {
      return GetFrame(0);
    }

    /**
		 * Gets the "Netscape" iteration count, if any.
		 * A count of 0 means repeat indefinitiely.
		 *
		 * @return iteration count if one was specified, else 1.
		 */

    public int GetLoopCount()
    {
      return loopCount;
    }

    /**
		 * Creates new frame image from current data (and previous
		 * frames as specified by their disposition codes).
		 */

    /**
		 * Gets the image contents of frame n.
		 *
		 * @return BufferedImage representation of frame, or null if n is invalid.
		 */

    public Image GetFrame(int n)
    {
      Image im = null;
      if ((n >= 0) && (n < frameCount))
      {
        im = ((GifFrame)frames[n]).image;
      }
      return im;
    }

    /**
		 * Gets image size.
		 *
		 * @return GIF image dimensions
		 */

    public Size GetFrameSize()
    {
      return new Size(width, height);
    }

    /**
		 * Reads GIF image from stream
		 *
		 * @param BufferedInputStream containing GIF file.
		 * @return read status code (0 = no errors)
		 */

    public int Read(Stream inStream)
    {
      Init();
      if (inStream != null)
      {
        this.inStream = inStream;
        ReadHeader();
        if (!Error())
        {
          ReadContents();
          if (frameCount < 0)
          {
            status = STATUS_FORMAT_ERROR;
          }
        }
        inStream.Close();
      }
      else
      {
        status = STATUS_OPEN_ERROR;
      }
      return status;
    }

    /**
		 * Reads GIF file from specified file/URL source  
		 * (URL assumed if name contains ":/" or "file:")
		 *
		 * @param name String containing source
		 * @return read status code (0 = no errors)
		 */

    public int Read(String name)
    {
      status = STATUS_OK;
      try
      {
        name = name.Trim().ToLower();
        status = Read(new FileInfo(name).OpenRead());
      }
      catch (IOException)
      {
        status = STATUS_OPEN_ERROR;
      }

      return status;
    }

    protected void SetPixels()
    {
      // expose destination image's pixels as int array
      //		int[] dest =
      //			(( int ) image.getRaster().getDataBuffer()).getData();
      int[] dest = GetPixels(bitmap);

      // fill in starting image contents based on last image's dispose code
      if (lastDispose > 0)
      {
        if (lastDispose == 3)
        {
          // use image before last
          int n = frameCount - 2;
          if (n > 0)
          {
            lastImage = GetFrame(n - 1);
          }
          else
          {
            lastImage = null;
          }
        }

        if (lastImage != null)
        {
          //				int[] prev =
          //					((DataBufferInt) lastImage.getRaster().getDataBuffer()).getData();
          int[] prev = GetPixels(new Bitmap(lastImage));
          Array.Copy(prev, 0, dest, 0, width * height);
          // copy pixels

          if (lastDispose == 2)
          {
            // fill last image rect area with background color
            Graphics g = Graphics.FromImage(image);
            Color c = Color.Empty;
            if (transparency)
            {
              c = Color.FromArgb(0, 0, 0, 0); // assume background is transparent
            }
            else
            {
              c = Color.FromArgb(lastBgColor);
              //						c = new Color(lastBgColor); // use given background color
            }
            Brush brush = new SolidBrush(c);
            g.FillRectangle(brush, lastRect);
            brush.Dispose();
            g.Dispose();
          }
        }
      }

      // copy each source line to the appropriate place in the destination
      int pass = 1;
      int inc = 8;
      int iline = 0;
      for (int i = 0; i < ih; i++)
      {
        int line = i;
        if (interlace)
        {
          if (iline >= ih)
          {
            pass++;
            switch (pass)
            {
              case 2:
                iline = 4;
                break;
              case 3:
                iline = 2;
                inc = 4;
                break;
              case 4:
                iline = 1;
                inc = 2;
                break;
            }
          }
          line = iline;
          iline += inc;
        }
        line += iy;
        if (line < height)
        {
          int k = line * width;
          int dx = k + ix; // start of line in dest
          int dlim = dx + iw; // end of dest line
          if ((k + width) < dlim)
          {
            dlim = k + width; // past dest edge
          }
          int sx = i * iw; // start of line in source
          while (dx < dlim)
          {
            // map color and insert in destination
            int index = pixels[sx++] & 0xff;
            int c = act[index];
            if (c != 0)
            {
              dest[dx] = c;
            }
            dx++;
          }
        }
      }
      SetPixels(dest);
    }

    /**
		 * Decodes LZW image data into pixel array.
		 * Adapted from John Cristy's ImageMagick.
		 */

    protected void DecodeImageData()
    {
      int NullCode = -1;
      int npix = iw * ih;
      int available, clear, code_mask, code_size, end_of_information, in_code, old_code, bits, code, count, i, datum, data_size, first, top, bi, pi;

      if ((pixels == null) || (pixels.Length < npix))
      {
        pixels = new byte[npix]; // allocate new pixel array
      }
      if (prefix == null)
        prefix = new short[MaxStackSize];
      if (suffix == null)
        suffix = new byte[MaxStackSize];
      if (pixelStack == null)
        pixelStack = new byte[MaxStackSize + 1];

      //  Initialize GIF data stream decoder.

      data_size = Read();
      clear = 1 << data_size;
      end_of_information = clear + 1;
      available = clear + 2;
      old_code = NullCode;
      code_size = data_size + 1;
      code_mask = (1 << code_size) - 1;
      for (code = 0; code < clear; code++)
      {
        prefix[code] = 0;
        suffix[code] = (byte)code;
      }

      //  Decode GIF pixel stream.

      datum = bits = count = first = top = pi = bi = 0;

      for (i = 0; i < npix;)
      {
        if (top == 0)
        {
          if (bits < code_size)
          {
            //  Load bytes until there are enough bits for a code.
            if (count == 0)
            {
              // Read a new data block.
              count = ReadBlock();
              if (count <= 0)
                break;
              bi = 0;
            }
            datum += (block[bi] & 0xff) << bits;
            bits += 8;
            bi++;
            count--;
            continue;
          }

          //  Get the next code.

          code = datum & code_mask;
          datum >>= code_size;
          bits -= code_size;

          //  Interpret the code

          if ((code > available) || (code == end_of_information))
            break;
          if (code == clear)
          {
            //  Reset decoder.
            code_size = data_size + 1;
            code_mask = (1 << code_size) - 1;
            available = clear + 2;
            old_code = NullCode;
            continue;
          }
          if (old_code == NullCode)
          {
            pixelStack[top++] = suffix[code];
            old_code = code;
            first = code;
            continue;
          }
          in_code = code;
          if (code == available)
          {
            pixelStack[top++] = (byte)first;
            code = old_code;
          }
          while (code > clear)
          {
            pixelStack[top++] = suffix[code];
            code = prefix[code];
          }
          first = suffix[code] & 0xff;

          //  Add a new string to the string table,

          if (available >= MaxStackSize)
            break;
          pixelStack[top++] = (byte)first;
          prefix[available] = (short)old_code;
          suffix[available] = (byte)first;
          available++;
          if (((available & code_mask) == 0) && (available < MaxStackSize))
          {
            code_size++;
            code_mask += available;
          }
          old_code = in_code;
        }

        //  Pop a pixel off the pixel stack.

        top--;
        pixels[pi++] = pixelStack[top];
        i++;
      }

      for (i = pi; i < npix; i++)
      {
        pixels[i] = 0; // clear missing pixels
      }
    }

    /**
		 * Returns true if an error was encountered during reading/decoding
		 */

    protected bool Error()
    {
      return status != STATUS_OK;
    }

    /**
		 * Initializes or re-initializes reader
		 */

    protected void Init()
    {
      status = STATUS_OK;
      frameCount = 0;
      frames = new ArrayList();
      gct = null;
      lct = null;
    }

    /**
		 * Reads a single byte from the input stream.
		 */

    protected int Read()
    {
      int curByte = 0;
      try
      {
        curByte = inStream.ReadByte();
      }
      catch (IOException)
      {
        status = STATUS_FORMAT_ERROR;
      }
      return curByte;
    }

    /**
		 * Reads next variable length block from input.
		 *
		 * @return number of bytes stored in "buffer"
		 */

    protected int ReadBlock()
    {
      blockSize = Read();
      int n = 0;
      if (blockSize > 0)
      {
        try
        {
          int count = 0;
          while (n < blockSize)
          {
            count = inStream.Read(block, n, blockSize - n);
            if (count == -1)
              break;
            n += count;
          }
        }
        catch (IOException) {}

        if (n < blockSize)
        {
          status = STATUS_FORMAT_ERROR;
        }
      }
      return n;
    }

    /**
		 * Reads color table as 256 RGB integer values
		 *
		 * @param ncolors int number of colors to read
		 * @return int array containing 256 colors (packed ARGB with full alpha)
		 */

    protected int[] ReadColorTable(int ncolors)
    {
      int nbytes = 3 * ncolors;
      int[] tab = null;
      byte[] c = new byte[nbytes];
      int n = 0;
      try
      {
        n = inStream.Read(c, 0, c.Length);
      }
      catch (IOException) {}
      if (n < nbytes)
      {
        status = STATUS_FORMAT_ERROR;
      }
      else
      {
        tab = new int[256]; // max size to avoid bounds checks
        int i = 0;
        int j = 0;

        while (i < ncolors)
        {
          uint r = ((uint)c[j++]) & 0xff;
          uint g = ((uint)c[j++]) & 0xff;
          uint b = ((uint)c[j++]) & 0xff;
          tab[i++] = (int)(0xff000000 | (r << 16) | (g << 8) | b);
        }
      }
      return tab;
    }

    /**
		 * Main file parser.  Reads GIF content blocks.
		 */

    protected void ReadContents()
    {
      // read GIF file content blocks
      bool done = false;
      while (!(done || Error()))
      {
        int code = Read();
        switch (code)
        {
          case 0x2C: // image separator
            ReadImage();
            break;

          case 0x21: // extension
            code = Read();
            switch (code)
            {
              case 0xf9: // graphics control extension
                ReadGraphicControlExt();
                break;

              case 0xff: // application extension
                ReadBlock();
                String app = "";
                for (int i = 0; i < 11; i++)
                {
                  app += (char)block[i];
                }
                if (app.Equals("NETSCAPE2.0"))
                {
                  ReadNetscapeExt();
                }
                else
                  Skip(); // don't care
                break;

              default: // uninteresting extension
                Skip();
                break;
            }
            break;

          case 0x3b: // terminator
            done = true;
            break;

          case 0x00: // bad byte, but keep going and see what happens
            break;

          default:
            status = STATUS_FORMAT_ERROR;
            break;
        }
      }
    }

    /**
		 * Reads Graphics Control Extension values
		 */

    protected void ReadGraphicControlExt()
    {
      Read(); // block size
      int packed = Read(); // packed fields
      dispose = (packed & 0x1c) >> 2; // disposal method
      if (dispose == 0)
      {
        dispose = 1; // elect to keep old image if discretionary
      }
      transparency = (packed & 1) != 0;
      delay = ReadShort() * 10; // delay in milliseconds
      transIndex = Read(); // transparent color index
      Read(); // block terminator
    }

    /**
		 * Reads GIF file header information.
		 */

    protected void ReadHeader()
    {
      String id = "";
      for (int i = 0; i < 6; i++)
      {
        id += (char)Read();
      }
      if (!id.StartsWith("GIF"))
      {
        status = STATUS_FORMAT_ERROR;
        return;
      }

      ReadLSD();
      if (gctFlag && !Error())
      {
        gct = ReadColorTable(gctSize);
        bgColor = gct[bgIndex];
      }
    }

    /**
		 * Reads next frame image
		 */

    protected void ReadImage()
    {
      ix = ReadShort(); // (sub)image position & size
      iy = ReadShort();
      iw = ReadShort();
      ih = ReadShort();

      int packed = Read();
      lctFlag = (packed & 0x80) != 0; // 1 - local color table flag
      interlace = (packed & 0x40) != 0; // 2 - interlace flag
      // 3 - sort flag
      // 4-5 - reserved
      lctSize = 2 << (packed & 7); // 6-8 - local color table size

      if (lctFlag)
      {
        lct = ReadColorTable(lctSize); // read table
        act = lct; // make local table active
      }
      else
      {
        act = gct; // make global table active
        if (bgIndex == transIndex)
          bgColor = 0;
      }
      int save = 0;
      if (transparency)
      {
        save = act[transIndex];
        act[transIndex] = 0; // set transparent color if specified
      }

      if (act == null)
      {
        status = STATUS_FORMAT_ERROR; // no color table defined
      }

      if (Error())
        return;

      DecodeImageData(); // decode pixel data
      Skip();

      if (Error())
        return;

      frameCount++;

      // create new image to receive frame data
      //		image =
      //			new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB_PRE);

      bitmap = new Bitmap(width, height);
      image = bitmap;
      SetPixels(); // transfer pixel data to image

      frames.Add(new GifFrame(bitmap, delay)); // add image to frame list

      if (transparency)
      {
        act[transIndex] = save;
      }
      ResetFrame();
    }

    /**
		 * Reads Logical Screen Descriptor
		 */

    protected void ReadLSD()
    {
      // logical screen size
      width = ReadShort();
      height = ReadShort();

      // packed fields
      int packed = Read();
      gctFlag = (packed & 0x80) != 0; // 1   : global color table flag
      // 2-4 : color resolution
      // 5   : gct sort flag
      gctSize = 2 << (packed & 7); // 6-8 : gct size

      bgIndex = Read(); // background color index
      pixelAspect = Read(); // pixel aspect ratio
    }

    /**
		 * Reads Netscape extenstion to obtain iteration count
		 */

    protected void ReadNetscapeExt()
    {
      do
      {
        ReadBlock();
        if (block[0] == 1)
        {
          // loop count sub-block
          int b1 = block[1] & 0xff;
          int b2 = block[2] & 0xff;
          loopCount = (b2 << 8) | b1;
        }
      } while ((blockSize > 0) && !Error());
    }

    /**
		 * Reads next 16-bit value, LSB first
		 */

    protected int ReadShort()
    {
      // read 16-bit value, LSB first
      return Read() | (Read() << 8);
    }

    /**
		 * Resets frame state for reading next image.
		 */

    protected void ResetFrame()
    {
      lastDispose = dispose;
      lastRect = new Rectangle(ix, iy, iw, ih);
      lastImage = image;
      lastBgColor = bgColor;
      //		int dispose = 0;
      //bool transparency = false;
      //int delay = 0;
      lct = null;
    }

    /**
		 * Skips variable length blocks up to and including
		 * next zero length block.
		 */

    protected void Skip()
    {
      do
      {
        ReadBlock();
      } while ((blockSize > 0) && !Error());
    }

    private int[] GetPixels(Bitmap bitmap)
    {
      int[] pixels = new int[3 * image.Width * image.Height];
      int count = 0;
      for (int th = 0; th < image.Height; th++)
      {
        for (int tw = 0; tw < image.Width; tw++)
        {
          Color color = bitmap.GetPixel(tw, th);
          pixels[count] = color.R;
          count++;
          pixels[count] = color.G;
          count++;
          pixels[count] = color.B;
          count++;
        }
      }
      return pixels;
    }

    private void SetPixels(int[] pixels)
    {
      int count = 0;
      for (int th = 0; th < image.Height; th++)
      {
        for (int tw = 0; tw < image.Width; tw++)
        {
          Color color = Color.FromArgb(pixels[count++]);
          bitmap.SetPixel(tw, th, color);
        }
      }
    }

    #region Nested type: GifFrame

    public class GifFrame
    {
      public Image image;
      public int delay;

      public GifFrame(Image im, int del)
      {
        image = im;
        delay = del;
      }
    }

    #endregion
  }
}